Edge fluctuations and global confinement with lower hybrid current drive in the ASDEX tokamak

Abstract

The aim of this report is to investigate simultaneously the level of edge electrostatic fluctuations and the global particle/energy confinement for a well-defined, low-density LHCD regime on ASDEX. Attention is focused on the variation of these quantities with LH power to study the transition from improved to deteriorated confinement in more detail. The experimental arrangement and details of measurement of the edge electrostatic fluctuations by Langmuir probes are first of all described. The LHCD regime is documented and the behaviour of the global energy/particle confinement during the LH power scan is demonstrated. Evolution of the edge fluctuations under the same discharge conditions is also discussed and a summary of the results is presented.